1. Field of the Invention
The present invention relates to a new and useful class of corrosion inhibitors, and a process of using them. More particularly, the present invention concerns novel compositions of matter which reduce the attack of aqueous acid solutions on ferrous metals at high temperatures, and a process of using them.
2. Technology Review
In the exploration and recovery of oil from underground fields, it is common to "acidize" both new and producing wells with aqueous solutions of strong acids. Various inhibitors for preventing the attack of acids on ferrous metals have been proposed. Of the many inhibitors especially designed to prevent acid attack on the well casings, very few provide satisfactory protection at high temperatures. Arsenic and/or various arsenic compounds were used as corrosion inhibitors, despite their toxic effect. The toxic nature of arsenic and its compounds, and their adverse effect on catalysts used in petroleum refineries, have caused an extensive search for new corrosion inhibitors.
U.S. Pat. No. 4,028,268 discloses specific high-temperature corrosion inhibitors comprising a quaternized derivative of quinoline and a halomethylated polycyclic compound, an acetylenic alcohol, a surface active agent, and a formic acid derivative. Inhibitors prepared from quinoline and aliphatic and single-ring aromatic compounds are surprisingly less effective (col. 9, lines 11 to 18).
U.S. Pat. No. 3,658,720 discloses corrosion inhibitors comprising at least two acetylenic alcohols, a quinoline quaternary compound, and an organic fluoride, which cooperate to reduce the corrosivity of corrosive acids.
Schmitt and Bedbur disclose a study by AC impedance measurements of pyridinium and quinolinium derivatives in an investigation of structural and electronic effects in acid inhibitors. Werkstoffe und Korrosion, volume 36, pages 273-278 (1985).
It would be desirable to have a corrosion inhibitor which is useful in a broader number of situations. For example, highly concentrated hydrochloric acid is often employed in oil well stimulation treatment, but its use can lead to severe corrosion problems, especially at high temperatures. Thus, it would be desirable to have a corrosion inhibitor composition which could inhibit the acid corrosion of ferrous metals even in the presence of concentrated hydrocholoric acid at high temperatures and which is compatible with a variety of additives, for example, surfactants.